I have two object one is flatten obj and another is unflatten. I need to override flatten object with flat object if the level is same..

example

const b = {

  "customerDetails": {
    "freight_forwarder": null,
    "account_holder": null,
  },
}
const a= {
  
  "customerDetails.freight_forwarder": {
    "label": "APL ",
    "value": "4c4bb555-154f-4e84-ab07-641d6dd37c4e"
  },
  "customerDetails.account_holder": {
    "label": "AAR",
    "value": "4cd309f5-66d5-459f-a06e-9b52298a87b3"
  },

}




console.log({
    ...b,
    ...a
})

current output

{
  "customerDetails": {
    "freight_forwarder": null,
    "account_holder": null
  },
  "customerDetails.freight_forwarder": {
    "label": "APL ",
    "value": "4c4bb555-154f-4e84-ab07-641d6dd37c4e"
  },
  "customerDetails.account_holder": {
    "label": "AAR",
    "value": "4cd309f5-66d5-459f-a06e-9b52298a87b3"
  }
}

expected output :

{
  "customerDetails.freight_forwarder": {
    "label": "APL ",
    "value": "4c4bb555-154f-4e84-ab07-641d6dd37c4e"
  },
  "customerDetails.account_holder": {
    "label": "AAR",
    "value": "4cd309f5-66d5-459f-a06e-9b52298a87b3"
  }
}

shall I flatten the first OBJECT ?? or any other way ?